Mantis Shrimp: A Deceptive Foe
Biology 342 Fall 2012
Will Horner, Jules Weinstein
Introduction
Picture from http://planetanimalzone.blogspot.com.
Mantis Shrimp Background
Mantis shrimp (Stomatopods) are an extremely interesting and unique order of crustaceans. A novel mechanism in their claws, a raptorial appendage, allows them to strike quickly with immense force to stun or kill prey. Some species stab their victims, while others pummel them to crack their shells. However, as a result of a potentially intense and violent lifestyle, stomatopods suffer injuries to their tough carapace and need to molt, much like other arthropods. Unfortunately for the stomatopod, molting has a dangerous twist: not only is their carapace weakened, but their devastating weapons offline for the duration of the process. This gives rise to the practice of aggressive threat displays; not only do they minimize casualties by replacing dangerous conflict with ritualized fighting, but vulnerable molters are given a fighting chance!
Arm diagram from http://arthropoda.southernfriedscience.com
Video from Youtube.com. Produced by National Geographic.
Drawing from http://www.naturalhistorymag.com.
False Threat Displays
When molting, a stomatopod will attempt to threat more frequently, as it knows its own weakness. This is necessitated by its appendages literally tearing off the animal if it attempts to use them without solidifying its carapace. Evolutionarily the stomatopod is encouraged to engage in non-lethal combat. This trend is supported by population models and through observation. There is also a significant portion of learning involved in the activities of the stomatopod. The false threats themselves can be studied from many different angles, among them the phylogenetic and ontogenetic origins of the behavior. Not only has the behavior evolved, but it developes over the mantis shrimp's life. Furthermore, the physical mechanism of the behavior and the survival value that the false threat has for the mantis shrimp are also important tools in understanding the true purpose of this unique display.